Jest test.each with object property in name [duplicate] - jestjs

Question

Is it possible to access an object's key inside the name portion of a .each?
let accounts =
[
{
details:
{
company_name:
"company_name",
email,
password:
"asdf",
},
find:
[
"_id",
"company_name",
"email",
"type",
],
type:
"creator"
},
{
details:
{
email,
first_name:
"first_name",
last_name:
"last_name",
password:
"asdf",
},
find:
[
"_id",
"email",
"first_name",
"last_name",
"type",
],
type:
"user"
},
]
describe.each(accounts)(
"%s", // <-- access the 'type' key, e.g. account.type
function (account)
{
// test code
}
)

Answer 1

Jest describe.each expects an array of arrays in the first parameter. If you pass in a 1D array, internally it will be mapped to an array of arrays (i.e. passing [1, 2, 3] as first parameter would be converted to [[1], [2], [3]]).
Each one of the arrays inside of the array is used as the data for a test suite. So, in the previous example, describe.each would generate three test suites, the first with 1 as data, the second with 2 as data and the third with 3 as data.
Now, in the test suite name, you can only format the parameters you are providing to it. In your case, you are passing to each test suite the data in each object of the accounts array. So, when you set the format specifiers in the test suite name, they will apply to the whole account object (i.e. the %s in your example will stringify your object resulting in [object Object]). Unfortunately, I don't think you can apply the format specifiers to a key of the object.
Some ideas to accomplish what you want:
Solution 1
If you use the %s formatter to compose the test suite name, the toString method of Object will be called (which by default returns [object Object]).
If you define a toString method in each of your accounts objects, that method will be used instead. So, we could add the toString method to each one of the account objects with this code (note that the toString method we are adding is returning the value for the type key):
const accounts = [{
details: {
company_name: "company_name",
email: "aa",
password: "asdf",
},
find: [ "_id", "company_name", "email", "type", ],
type: "creator"
}, {
details: {
email: 'bb',
first_name: "first_name",
last_name: "last_name",
password: "asdf",
},
find: [ "_id", "email", "first_name", "last_name", "type", ],
type: "user"
}].map(account => Object.assign(account, { toString: function() { return this.type; } }));
Now, with the %s format specifier you should see the account type in each test suite:
describe.each(accounts)(
"%s", // <-- This will cause the toString method to be called.
function (account)
{
// test code
}
)
Solution 2
You can always redefine each one of your test suite data so that the first parameter is the account type (note that now accounts is a 2D array):
let accounts = [
[
"creator",
{
details: {
company_name: "company_name",
email: "email",
password: "asdf",
},
find: [ "_id", "company_name", "email", "type", ],
type: "creator"
}
], [
"user",
{
details: {
email: "email",
first_name: "first_name",
last_name: "last_name",
password: "asdf",
},
find: [ "_id", "email", "first_name", "last_name", "type", ],
type: "user"
},
]
]
You can now use that first parameter (which is the account type) to give the test suite its name:
describe.each(accounts)(
'%s', // <-- This %s will format the first item in each test suite array.
function (accountType, account) {
// test code
}
);
Note that now your test function receives two parameters as each test suite array has two elements. The first one is the account type and the second one is the account data.
Solution 3
You can use the tagged template literal form of describe.each. With this solution you don't have to change your current definition of accounts array.
describe.each`
account
${accounts[0]}
${accounts[1]}
`('$account.type', function (account) {
// test code
});
The downside of this solution is that you have to manually append each test suite data in the template literal in a new line (i.e. if you add a new element to the accounts array you have to remember to add it in the template literal in a new line as ${accounts[2]}).

Answer 2

you can map your initial account array to convert each account into an array with 2 items:
the account type
the initial account element
Now, you can use the first element array in describe name
describe.each(accounts.map(account => [account.type, account]))(
'testing %s', // %s replaced by account type
(type, account) => { // note: 2 arguments now
it('details should be defined ', () => {
expect(account.details).toBeDefined();
});
},
);

Answer 3

As modern doc says, you can
generate unique test titles by injecting properties of test case object with $variable
So simply:
describe.each(accounts)(
"$type",
function (account) {
// tests
}
)
You can access nested object values like this: $variable.path.to.value
The same works on test.each level.

Answer 4

I had a similar problem with an object. I wanted to test an error message depending on http error codes, so I wrote a test object like so:
const expectedElements = {
error: {
code: 500,
title: "Problème avec l'API"
},
notFound:{
code: 404,
title: "Élement absent"
},
unauthorized:{
code: 401,
title: "Accès non autorisé"
}
};
I used Object.entries(obj) to get an array with those entries written like so: ['key','value']. I can access thoses as two parameters in the test. Here's how I wrote it:
test.each(Object.entries(expectedElements))("NoAccess show the right element for %s",(key,expectedElement)=>{
const { getByRole } = render(<NoAccess apiStatusCode={expectedElement.code}/>);
//test code
});
Now I can add cases as much as I want and I won't have to rewrite the test or create an array. I just write an new value in my expectedElements object. Bonus, I also have a descriptive test name!

Answer 5

Another alternative is to create a wrapper class and stick to a simple convention:
class TestCase {
constructor(value) {
this._value = value;
}
get value() {
return this._value;
}
toString() {
return JSON.stringify(this._value);
}
}
Then a test will look like this:
const testCases = accounts.map(TestCase)
describe.each(accounts)(
"%s", // <-- you can customize this in TestCase toString
function ({value: account})
{
// test code
}
)